page 99 of 412 manual function number 981 this is the input output verification for troubleshooting. look for the led segment that corresponds to tb1-83 which is the output transistor for the BP circuit. if the car attempts to run, and the corresponding led for tb1-83 lights up, then the dsd412 is initiating the output, this way you can tell if the output should be coming on, if led is lit, and output not on, then bad transistor output,